Hygroscopic acrylic synthetic fibers and method for preparing the same

ABSTRACT

Acrylonitrile polymer fibers having an improved hygroscopicity are prepared by hydrolyzing an acrylonitrile copolymer comprising 0.5 to 10% by weight of N,N-substituted amide, 0 - 15% by weight of an ethylenically unsaturated compound copolymerizable with acrylonitrile and at least 85% by weight of acrylonitrile in nitric acid to give a degree of hydrolysis as expressed by ODR of 1680 cm 1 to 1450 cm 1 in the range of 1.2 - 1.8, followed by conventional wet spinning by using nitric acid as a solvent.

United States Patent Ohfuka et a1.

[ Dec. 16, 1975 PERCENT TRANSMITTANCE (70) HYGROSCOPIC ACRYLIC SYNTHETICFIBERS AND METHOD FOR PREPARING THE SAME Inventors: Toshio Ohfuka;Yoshihisa Schichijo;

Yasushi Ichikawa; Katsuo Yamamoto, all of Fuji, Japan Asahi Kasei KogyoKabushika Kaisha, Osaka, Japan Filed: Sept. 6, 1973 Appl. No.: 394,937

Related US. Application Data Continuation-in-part of Ser. No. 138,875,April 30, 1971, abandoned, which is a continuation-in-part of Ser. No.30,540, April 20, 1970, abandoned.

Assignee:

Foreign Application Priority Data May 8, 1969 Japan 44-34782 U.S.C1.260/85.5 S; 260/855 R; 260/855 AM;

260/855 N; 260/855 B; 260/8072; 260/65; 260/8073; 260/793 M; 260/63 NInt. C1. C08F 220/48; C08F 224/; C08F 226/06 Field of Search. 260/855 R,85.5 AM, 85.5 N, 260/855 B, 80.72, 80.73, 85.55

[56] References Cited UNITED STATES PATENTS 2,579,451 12/1951 Polson264/182 3,073,669 1/1963 Fujisaki et a1. 264/182 3,107,971 10/1963Yasawa et a1 264/182 3,147,322 9/1964 Fujisaki et a1. 264/182 3,287,30411/1966 Fujisaki et a1 260/296 AN 3,399,161 8/1968 Ichikawa et a1264/182 3,410,941 11/1968 Dagon 264/182 Primary Examiner.1oseph L.Schofer Assistant ExaminerMaria S. Tungol Attorney, Agent, or Firm-FredPhilpitt [57] ABSTRACT Acrylonitrile polymer fibers having an improvedbygroscopicity areprepared by hydrolyzing an acrylonitrile copolyrnercomprising 0.5 to 10% by weight of N,N-substituted amide, 0 by weight ofan ethylenically unsaturated compound copolymerizable with acrylonitrileand at least by weight of acrylonitrile in nitric acid to give a degreeof hydrolysis as expressed by ODR of 1680 cmto 1450 cm-' in the range of1.2-1.8,.f0l1owed by conventional wet spinning by using nitric acid as asolvent.

2 Claims, 3 Drawing Figures INFRARED ABSORPTION SPECTRUM WAVE NUMBERS-U.S. Patent Dec; 16, 1975 Sheet 1 of2 3,926,930

FIG.

INFRARED ABSORPTION SPECTRUM \|3'0o\||'00 \9'00 \700 \500 I600 I400 I200I000 800 600 O O O O O O 6 5 4 3 2 I.

WAVE NUMBERS (cm') US. Patent INFRARED ABSORPTION SPECTRUM ABSORBANCE4000 3500 3000 2500 I I900? I700 I I500 I500 I100 \900 3700 I 500 2000I800 I600 I400 I200 WAVE NUMBERS TANGENT TANGENT WAVE NUMBERS (Cm'I-IYGROSCOPIC ACRYLIC SYNTHETIC FIBERS :AND METHOD FOR PREPARING THESAME This application is a continuation-in-part application of Ser. No.138,875, filed Apr. 30, 1971, which in turn is a continuation-in-part ofSer. No. 30,540,'filed Apr. 20,-1970. Both applications are nowabandoned. The benefits of 35 USC 120 are claimed with respect to theseprior related applications.

DESCRIPTION OF THE INVENTION fibers, because they are widely applied tosuch articles as underwear. baby wear, socks, blankets, etc. Theacrylonitrile fibers containing acrylonitrile as a main component haveexcellent physical and chemical properties, but their hygroscopicity isespecially small among the various fibers and this is a great practicaldisadvantage.

Many attempts have been made to improve the hygroscopicity of theacrylonitrile polymer fibers, but acrylonitrile polymer fibers having ahygroscopicity comparable with that of the natural fibers, and at thesame time, sufficient practical functions as a fiber, have not beendiscovered yet.

So far proposed hygroscopic synthetic fibers have been prepared bysubjecting fibers or knitted or woven cloth, to resin treatment,chemical treatment or graft polymerization of hydrophilic monomers.However, glutinous cohesion between fibers is liable to take place, andthe shape, gloss, whiteness, feeling and touch of the fibers areconsiderably impaired. Waterabsorbing property may be endowed thereby,but the true hygroscopicity or permanency is impaired.

Further, in a method for mixing polymers or a spinning dope withahydrophilic substance or hygroscopic substance, there are'only a smallnumber of suitable substances and the permanency has not been satisfied.The spinnability, gloss, feeling and touch have been inevitably lowered.

Furthermore, in the case of fibers composed of a copolymer with ahydrophilic ethylenic unsaturated compound containing a carboxylic-acid,sulfonic acid, amines and their salts hydroxyl group, primary amide,etc'. unless a large amount of hydrophilic compound is used,satisfactory hygroscopicity cannot be obtained 2 ability, etc., and agood fiber form. feeling. touch. physical properties and dyeability.

The acrylonitrile polymer fibers of the present invention compriseacrylonitrile polymer fibers having a moisture regain of 3.0% to 10.0%at a relative humidity of 65% at 20C, and consist of a nitricacid-hydrolyzate of a polymer comprising at least by weight ofacrylonitrile, 05-10% by weight of N,N-substituted acrylormethacrylamide having the general formula of (wherein R represents ahydrogen atom or a methyl group; R and R represent alkyl groups having 1to 3 carbon atoms, the sum total of carbon atoms of R. and R being notmore than 4 or R and R being cyclically connected to each other to forma pyrrolidine or morpholine structure) and optionally a balance of anethylenically unsaturated compound copolymerizable with acrylonitrile,having such a degree of hydrolysis that an amide group of 1680 cm isformed in the infrared absorption spectrum and the ODR of 1680 cm to1450 cm is in the range of 1.2l.8.

It has been heretofore well known that acrylonitrile type polymers arehydrolyzed by an acid but hydrolysis greatly reduces the heat stabilityand mechanical properties of the polymers and also reduces spinnabilityat the time of fiber production. Accordingly, it has been a conventionalprocedure to suppress the tendency of hydrolysis as much as possible inprior art. We have found thatthe acrylonitrile copolymer with the amidesrepresented by a general formula (Ilcan be hydrolyzed quickly by an acidand its hydrophilic property can be improved thereby, and in spite ofsuch an advantage, the reduction of heat stability and physicalproperties are very small.

The hydrolysis of the copolymers of acrylonitrile with primary amide orsecondary amide such as acrylamide or methacrylamide, N-monosubstitutedacrylamide or N-monosubstituted methacrylamide which are considered tobe homologs of the amides of the general for.- mula (I), carried out byacid is very slow, improvement of hydrophilic property is small,reduction of heat stability, physical properties and spinnability arelarge (see Example 2).

When 05-10% by weight of the N,N-substituted acrylamide ormethacrylamide as represented by the structural formula (I) is containedin the copolymer, a good effect can beattained according to the presentinvention. If the copolymer contains less than 0.5% by weight ofN,N-substituted acrylamide or methacrylamide, the increase in thehydrophilic property is small. If the copolymer contains more than 10%by weight of N,N-substituted acrylamide or methacrylamide, the reductionof physical properties becomes larger and practical functions as fibersare lowered. Therefore, the use of the copolymer containing less than0.5% or more than 10% by weight of N,N-substituted acrylamide ormethacrylamide is not preferable.

Furthermore, when the copolymer contains less than 85% by weight ofacrylonitrile, good physical and chemical properties of acrylonitrilepolymer fibers cannot be obtained.

erty of the polymer is lowered. Therefore I to 4 carbon 5 atoms arepreferable.

Amides in case where both of R. and R or either R or R ofN.N-substituted (meth) acrylamide of the formula I) is hydrogen atom.for example, acrylamide.

methacrylamide, N-methylacrylamide, N-methylmethacrylamide, etc. haveonly a small hydrolysis rate in an acid, and therefore improvement ofhygroscopicity is poor, and furthermore the thus obtained fibers showpoor heat stability and undergo considerable discoloration. andimpairment of physical properties resulting in notable degradation ofpractical functions as fibers. The N.N-substituted acrylamides ormethacrylamides represented by the structural formula (I) in the presentinvention include the following compounds:

CH CHCOl\l(CH;,) (N.N-dimethylacrylamideJ CH CCON(CH,(N.N-dimethylmethacrylamideJ CH1! CH CHCON (N-methyLN-ethylacrylamide)C:H CH3 1; CH CCON (N-methyl-N-ethyl- H methacrylamide) CH;- CHCON(C-H.-,): (N.N-diethylacrylamide) Of course, it is possible to copolymerizeother kinds of ethylenically unsaturated compounds with acrylonitrileand a compound represented by the general formula (I) in a balancedamount.

Examples of the ethylenic unsaturated compounds copolymerizable withacrylonitrile used in the present invention include alkyl acrylates suchas methyl acrylate, ethyl acrylate, etc.; alkyl methacrylates such asmethyl methacrylate, ethyl methacrylate, etc.; vinyl esters such asvinyl acetate; unsaturated ketones such as methylvinyl ketone, etc.;vinyl ethers; styrene and its alkyl derivatives; vinyl halides such asvinyl chloride,

vinyl fluoride, vinyl bromide, vinylidene chloride, etc.; vinylpyridinessuch as 2-vinylpyridine, 2-methyl-5- vinylpyridine, etc.;N,N-diethylaminoethyl methacrylates; sulfonic acids such asallylsulfonic acid, styrene sulfonic acid and their salts. I

The copolymers of the present invention canbe prepared according tovarious well known procedures, and there is no particular limitationthereto.

Even if the copolymers of N,N-substituted acrylamidc or methacrylamideas shown by the structural formula (l) and acrylonitrile of the presentinvention are spun using the well known solvents for the acrylonitrilepolymer other than concentrated acids. for example,

-N.N-dimethylformamide, N.N-dimethylacetamide, di-

methylsulfoxide, a concentrated aqueous solution of zinc chloride, aconcentrated aqueous solution of rhodanates, etc., no hydrolysis occurs,and hence improvement in the hygroscopicity of the thus obtained fiberscan scarcely be observed (reference is made to Example I).

This fact is due to the notable increase of hydrophilic property by thehydrolysis with acid, of the acrylonitrile polymers of the presentinvention.

As for acids, those other than nitric acid are also useful, but, fromthe viewpoint of solubility, spinnability. physical properties, etc.,nitric acid is most suitable.

FIG. I shows infrared absorption spectra of the copolymer used in thepresent invention.

FIG. 2 shows infrared absorption spectra of the fibers obtained byspinning a copolymer by wet process in a nitric acid system.

FIG. 3 is a figure illustrating ODR (optical density ratio) employed inthe present invention.

As shown in the infrared absorption spectra in FIGS. 1 and 2, when thecopolymers of the present invention are subjected to acid hydrolysis,the absorptions at 2250 cm and 1630 cm which are characteristicabsorptions of acrylonitrile and the amides represented by the generalformula (I), are reduced, and a new characteristic absorption which hasnot been observed before hydrolysis appears at I680 cm.

The hydrolysis mechanism and hydrolyzed product have not all beenclarified yet. However, it is presumed 5 from the fact that the nitrilegroups of the fibers after hydrolysis are less than those of theoriginal polymer, that the hydrolysis product be that formed by thereaction of the nitrile groups adjacent to the amide expressed by theformula (I), with the amide expressed by the formula (I), followed byhydrolysis. Further, in this hydrolysis, it is presumed that the amidesexpressed by the formula (I) are hydrolyzed easier than primary orsecondary amides, due to an autocatalysis in the pres-' ence of acid,since the electronegativity of the nitrogen atom of the N,N-substitutedamides expressed by the formula (I) is higher than those of primary orsecondary amides due to the electron inductive effect of the alkylgroup.

The characteristic absorption. at 1680 cm formed by the hydrolysis is inaccordancewith the characteristic absorption of acrylamide, but evenwhen it is assumed that the hydrolysis product be an acrylamide, and apolymer is prepared by copolymerizing acrylonitrile, acrylamide andN,N-dimethylacrylamide so as to give the infrared absorption spectra andabsorbance identical with those of the hydrolysisproduct of the presentinvention and the resulting polymer is spun with N,N-dimethylformamide,the moisture regain of the thus obtained fibers is remarkably smallerthan that of the hydrolysis product (see Comparative Example 1). Itseems from this fact that the hydrolysis product may be a hydrophilicsubstance other than the acrylamide, but even if it is acrylamide, thearrangement of the acrylamide formed by the hydrolysis in the polymerchain is different from that obtained by the copolymerization, whichresults in the difference of hygroscopic property and physicalproperties. Further, the homopolymer of the amide represented by thegeneral formula (I) hardly undergoes hydrolysis in contrast to itscopolymer with acrylonitrile. It is really surprising that the effect ofthe present invention can be attained only by the acid hydrolysis of thecopolymer of acrylonitrile and the amide represented by the generalformula (I).

In the hydrolysis of the copolymers of acrylonitrile and the amiderepresented by the general formula (I), of the present invention, thedegree of acid hydrolysis must be limited as hereinafter defined so'asto satisfy the object of the present invention. If the degree of acidhydrolysis is small, the increase of hygroscopicity is insufficient, anda. too large degree of acid hydrolysis is not preferable,becausephysical properties of fibers are reduced.

The degree of acidhydrolysis of Y the present invention can beexpressed'by the Optical Density Ratio (hereinafter referred to asODR)-of the characteristic absorption of the infrared spectrum.

Optical Density Ratio (ODR) is a ratio of optical densities of eachcharacteristicabsorption e.g. a ratio of log (b/a) log (d/c) in FIG. 3.In case of the present invention, the absorption of -CI-I 1450 cm, whichdoes not change before and after the hydrolysis, is selected as astandard value. The infrared absorption spectra herein referred to weremeasured using Hitachi ,GP-II type spectrograph according to KBr tabletmethod with the amount of sample of 2 mg/200 mgKBr.

As for the degree of hydrolysis in the present invention, it ispreferable that the ODR of absorption at 1680 cm, of amide formed byhydrolysis to absorption of methylene group at 1450 cm be in the rangeof 1.2 to 1.8. If ODR. is smaller than 1.2, the degree of hydrolysis isnot sufficient, hygroscopicity is low and not satisfactory for theobject of the present invention. If ODR is greater than 1.8, the amountof amide is larger, which results in the reduction of physicalproperties of fibers and degradation of heat stability. The degree ofhydro- 6. lysis in this range gives a moisture regain in the range of3.0-l0.0% at 20C and 65% RH.

Even in case of polymers other than the copolymers of acrylonitrile withamides expressed by the general formula (I), of the present invention,such as copolymer of acrylonitrile with acrylamide or acrylonitrilehomopolymer, it is possible to bring the ODR to a value in the range ofthe present invention by acid hydrolysis, but the resultant moistureregain is always low and does not reach the expected value of thepresent invention.

When the degree of hydrolysis is larger over the ODR value of thepresent invention. moisture regain greater than 3% can be attained butthe reduction of fiber properties is remarkable and degradation is sogreat that their commercial value is lost.

The hydrolysis conditions are selected depending upon the copolymerizedamount of the amide represented by the general formula (I) in thecopolymers of acrylonitrile with the amide represented by the generalformula (I).

As for the concentration of nitric acid, 55 is preferable. If it islower than 55%, the solubility of the copolymer is bad, and if it ishigher than 85%, whiteness of hydrolysis product becomes worse due toevolution of nitrous acid. This is not preferable.

As for the temperature of hydrolysis, when a temperature of 10C orhigher is selected. hydrolysis can be carried out using only a smallcopolymerized amount of the amide represented by the general formula of(I) and within a short period of time.

For the production of fibers, the nitric acid solution of hydrolysisproduct after the acid hydrolysis, as it is, can be used as a spinningsolution and a conventional nitric acid spinning process can beemployed.

Now, the present invention will be explained, referring tonon-limitative Examples.

Example I A. 3750 g. of acrylonitrile, 250 g. of N,N-dimethylacrylamideand 50 l of water were added to a 1 capacity polymerization reactor witha stirrer and mixed together. Then, 40 g. of ammonium persulfate and 200g. of sodium hydrogen sulfite were added thereto and the resultingmixture was adjusted to pH 2.8 with sulfuric acid. Then, thepolymerization reaction was carried out at 60C for 5 hours. Theresulting copolymer was thoroughly washed with water, dehydrated anddried at 70C for 10 hours.

The resulting polymer contained 94.3% by weight of acrylonitrile and5.7% by weight of N,N-dimethylacrylamide (polymer a The polymer (1 wasdissolved in 65% nitric acid at 0C to make its concentration 16% byweight. After the resulting solution was kept at 0C for 3 hours, thetemperature of the solution was elevated to 20C at which temperaturehydrolysis was carried out for 12 hours. Thereafter the solution wascooled to 5C, and then extruded from spinning nozzles 100 holes X 0.08mm) into a 30% aqueous nitric acid solution at 0C to coagulate theresulting extrudate. After water washing, the extruded fibers werestretched to 8 times the original length in boiling water and dried.Then, the fibers were subjected to wet heat treatment at C thereby toform fibers of 3 deniers.

Infrared absorption spectra of the polymer a and the fibers obtained bythe nitric acid hydrolysis and the wet spinning in the nitric acidsystem are given in FIGS. 1 and 2.

Separately, the polymer a was dissolved in dimethyl- -continuedforrnamide at 40C to give a concentration of 17% by (Acrykmimlc 943,7!weight. The resultmg solution was'extruded mm a 50% 9 aqueousdimethylformamide solution at 30C. washed d w1th water. stretched to 8times the original length in 5 Polymer e *AcrZvlnnitrile 100.11% boilingwater. dried and then subjected to wet heattreatment at 120C thereby toform fibers of 3 deniers. Each of these polymers was dissolved in 70%nitric a O y; z ggl i lzfi i i i g ggg fibers acid at 15C to glve aconcentration of 15% by weight. e I y O c are glven e 0 at whichtemperature hydrolysis was carried out for 18 hours. Thereafter theresulting solution was cooled to 0C and then extruded from spinningnozzles 100 Add Mfisture ODR holes X 0 08 mmda) into a 35% aqueousnitric acid at treatstrength strength regain (l680cm V Remarks q mm M M1 -1, 0 C to coagulate the extrudate. After water washmg,

the extruded fibers were stretched to 7 times the ori i- Example g 3m3,45 637 141 nal length 1n botlmg water, and dried. Then the fiberspresent were subjected to wet heat treatment at l 10C to form fibers of5 deniers. None 3.36 2.71 L88 0 tive The physical properties of theresulting fibers at C Example and 65% relative humidity were as follows:

Mois- ODR Dry Wet ture (l680cm"/ Hunter Polystrength strength regainl450cm) white- Remarks mer g/d g/d 71 ness Example of b 2.97 2.50 4.75[.44 63.5 the present invention c 2 83 2.26 3.99 1.02 56.7 ComparativeExample d 2.54 L89 2.78 1.60 49.2 Comparative Example e 2.02 1.43 .0l0.53 47.8 Comparative Example Hunters whiteness referred to in thepresent inven- 40 tion is given as follows: The fibers obtained by thehydrolysis were rich in Hunters whiteness 00 "(]0() L)2 gloss andflexibility and had a cool feeling when touched with hands wherein Lmeans brightness and a a is expressed by The moisture regain referred toin the present inveng fi tone of red'green and b by that of yellow' tionis iven accordin to the followin measurin method? g g g The fibersobtained from the polymer b of the present Fibers' of sample are scouredand then dried at invention were good in both moisture regain andwhiteand under a reduced pressure of 700 mm Hg till the ness whereas thefibers obtamfad from the C weight reaches a constant value. Theresulting dry and Polymer were. both. low m ODR and molsyure weight isweighed. After drying, the fibers are allowed regam and also bad mwhltenes' fibers obiamed to stand for one week in a desiccatorcontaining a satug g. p d L x. g regam and ratedaqueous solution ofsodium nitrite (RH. 65%). a m w 1 eness m Splte 0 lg Thereafter theweight is again weighed (wet weight). Example 3 Moisture regam is givenaccording to the following 5 Pol mers havm the followin com ositronswere equation. y g p prepared in the same manner as in Example 1:

(Wet weight (Dry weight f fibers offihgrs) r7 PolymerNN-dlmethylacrylamlde Acrylonltnle regam (Dry weight of fibers) g h 9.5%90.5% 1 11.9% 83.1%

Example 2 Polymers having the following compositions were Each Q thesfiP ym w j q 'f nitric acid prepared in the Same polymerization method asi E hydrolysis under the condltions described In the following Table,and then spun in the same manner as in ample 1:

N.N-dimeth vlmethacrylamide Example 1 to give fibers of 3 deniers. Thephysical properties of the resulting fibers at 20C and 65% relativehumidity are shown in the next Table.

Table Conditions Dry Wet ODR Moisture Hunters No. Polymer of strengthstrength l680cm"/ regain whiteness Remarks hydrolysis g/d g/d l450cm 1 f70% HNQ, 2.56 2.07 0.78 2.27 52.4 Comparative C 20hrs. Example 2 ditto70% HNO 2.11 1.53 1.11 2.62, 47.5 ditto C 20hrs. 3 ditto 70% HNQ, 1.621.02 1.45 2.93 42.1 ditto CX20hrs. 4 g HNO, 2.88 2.36 1.04 2.95 55.2ditto 20C 20hrs. 5 ditto 70% HNO 2.53 .27 1.29 3.51 52.3 Example of30CX20hrs. the present invention 6 h 65% HNQ 2.76 2.63 1.45 4.85 61.9ditto 10C Z0hrs. 7 ditto 65% HNO 2.59 2.32 1.59 8.05 60.1 ditto 20C20hrs. 8 r 65% HNQ, 2.48 1.97 1.73 6.25 60.7 Comparative 10C 20hrs.Example 9 ditto 65% HNO 2.11 1.69 1.82 7.98 58.3 ditto 15CX20hrsAccording to Experiments Nos. 1 and 2, the resulting fibers were low inboth ODR and moisture regain and also bad in whiteness due to the smallcopolymerized amount of the comonomer expressed by the general formula(I), in spite of the fact that they were hydrolysis products. As for No.3, the ODR was increased up to a given value of the present invention byemploying severe conditions of hydrolysis, but the moisture regain wasstill low due to the small copolymerized amount of the comonomerexpressed by the general formula (I), and a hydrolysis other than thatcaused by the structure of the formula (I) occurred due to the severeconditions of hydrolysis, which results in a higher ODR, butdegradations in the physical properties and whiteness were remarkable.As for No. 4, although the copolymerized amount of the comonomerexpressed by the general formula (I) fell within the range of thepresent invention, the ODR and moisture regain were both low due to thestill small copolymerized amount. Thus, the hydrolysis conditions mustbe made severer up to those of No. 5. However, when the copolymerizedamount of the comonomer expressed by the formula (I) is small, thewhiteness is reduced by the conditions of hydrolysis made severe due tothe small amount, and hence it is preferable that the copolymerizedamount is 3% or more. Nos. 6 and 7 are Examples of the presentinvention. As for No. 8, the ODR and moisture regain reached a givenvalue of the present invention due to the large copolymerized amount,but reduction in strength was great due to the large copolymerizedamount, and also the balance of performances of fibers was broken. Asfor No. 9, reduction in strength was similarly remarkable.

Example 4 A copolymer consisting of 93.7% by weight of acrylonitrile and6.3% by weight of acryloyl morpholine prepared in the same manner as inExample 1, was subjected to hydrolysis for 12 hours in a nitric acid at20C. After cooling, the resulting solution was extruded from spinningnozzles (100 holes X 0.06 mmtb) into a 35% nitric acid aqueous solutionto coagulate the extrudate. After water washing, the resulting fiberswere stretched to 7 times the original length by heating with steam.After drying, they were heat-treated at l 10C to obtain fibers of 2deniers. The physical properties of the resulting fibers at 20C and 65%relative humidity were as follows:

ODR 1.48 Moisture regain 7.15% Dr strength 3.03 Wet strength 2.76Hunter's 61.7

whiteness What is claimed is:

l. A polymer hydrolyzate produced by hydrolyzing with nitric acid apolymer comprising at least by weight of acrylonitrile, 0.5 10% byweight of N,N- substituted acrylor methacryl-amide having the generalformula of (wherein R represents a hydrogen atom or a methyl group; Rand R represent alkyl groups having 1 to 3 carbon atoms, the sum totalof carbon atoms of R and R being not more than 4, or R and R beingcyclically connected to each other to form a pyrrolidine or morpholinestructure) and 0 15% by weight of a compound selected from the groupconsisting of methyl acrylate. ethyl acrylate, methyl methacrylate,ethyl methacrylate, vinyl acetate, methyl vinyl ketone, styrene, vinylchloride, vinyl fluoride, vinyl bromide, vinylidene chloride,2-vinylpyridine, 2-methyl-5-vinylpyridine, N,N-diethylaminoethylmethacrylates, allysulfonic acid and styrene sulfonic acid, thehydrolysis being carried out to such a degree that an amide group of1680 cm is formed in the infrared absorption spectrum and the ODR of1680 cm to 1450 cm is in the range of 1.2 1.8, said polymer hydrolyzatehaving a moisture regain of 3.0 to 10% at a relative humidity of 65% at20C.

2. Fibers of acrylonitrile polymers according to claim 1 wherein saidN,N-substituted acrylor methacrylamide is N,N-dimethylacrylamide orN,N-dimethylmethacrylam ide.

1. A POLYMER HYDROLYZATE PRODUCED BY HYDROLYZING WITH NITRIC ACID APOLYMER COMPRISING AT LEAST 85% BY WEIGHT OF ACRYLONITRILE, 0.5-10% BYWEIGHT OF N,N-SUBSTITUTED ACRYL- OR METHYACRYL-AMIDE HAVING THE GENERALFORMULA OF
 2. Fibers of acrylonitrile polymers according to claim 1wherein said N,N-substituted acryl- or methacryl-amide isN,N-dimethylacrylamide or N,N-dimethylmethacrylamide.